I'm just going to go ahead and say it, GRRM is a terrible writer. Creative, but terrible.
He spends ages building up great characters and then bins them off at the drop of a hat, killing them in crappiest, non-entertaining way. He leaves so many plot-holes, it's infuriating.
Just because something is shocking and completely unexpected doesn't necessarily make it clever or good. Plot-twists should leave readers/watchers desperate for more, not piss them off so much that they might seriously stop reading/watching. He has no idea how to close off a plot-line, he just thinks "I'll just kill him/her" so he doesn't have to write stuff for that character anymore.
It's awful, people need to get out of his arse.